Apparatus for gun perforating well casing and surrounding unconsolidated formations



JR 2,559,687 ING WELL CASING AND ATED FORMATIONS y 1951 G. B. THOMAS,

APPARATUS FOR GUN PERFORAT SURROUNDING UNCONSOLID Filed M h 20 1945 INVENTOR. GERALD 5. moms, JR

ATTORNEY Patented July 10, :1951

APPARATUS FOR GUN PERFORATIN G WELL CASING AND SURROUNDING UNCONSOLI- DATED FORMATION S Gerald B. Thomas, Jr., United States Navy, Berkeley, Calif.

Application March 20, 1945, Serial No. 583,829

3 Claims. (Cl. 166- 1) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370' O. G. 757) This invention relates to apparatus for gun perforating unconsolidated fluid formations and more particularly to an arrangement for screening unconsolidated particles of an oil, gas or water formation from the interior of a casing in the formation while permitting flow of fluid from the formation to the casing.

Gun perforating of casing and fluid formations therearound is not new in the oil and gas industry in and of itself. There are now available conventional guns that may be lowered from the surface of the earth down a casing in a well to points adjacent the planes or formations of determined oil, gas or water strata. The guns are usually provided with electrical contacts for detonating cartridges and igniting powder to force projectiles out of the gun with sufficient force to penetrate the casing and a cement lining around the casing to permit fluids in the formation to flow intothe casing and allow recovery of the fluids by known processes and equipment. Gun perforating as a method of well completion is advantageous in combatting incursion of water into oil and gas strata and is also advantageous in shutting off gas in one stratum of a well from another stratum desired to be produced.

Likewise, it is simpler, by gun perforating completion of wells in separate zones of the same well in which a single string of pipe has been cemented, to effect individual completion and production of each stratum to its economic limit.

More precise control is also available by gun perforating wells in repressuring of the wells or by employing secondary recovery methods on the wells, such as by water flooding.

Notwithstanding the advantages of gun perforating, as such, the methods of gun perforating heretofore available could not be used in certain loose and unconsolidated oil, gas or water sands because the sand flowed into the casing with the fluid and the well sanded up.

The principal object of the present invention, therefore, is to provide for gun perforating wells without sanding them up.

Other objects of the invention are to provide for perforating well casing with their surrounding formations and screening sand from the fluid as the fluid passes from the formation to the casing; to weld a screen plug in the hole in the casing formed by the gun perforation in a novel manner; to separably combine a screen plug with a. projectile; to normally retain a projectile and plug together with a sleeve and peel off the sleeve just prior to welding the plug in the casing; and to provide improved steps in the method and arrangements of elements in the apparatus for the noted purposes.

In accomplishing these and other objects of the present invention, I have provided improved procedures and details of structure the preferred embodiments of which are hereinafter explained and illustrated in the accompanying drawing; wherein:

Figfll is a perspective view of an assembled projectile embodying the features of the present invention.

Fig. 2 is an elevational view of the screen plug end of the projectile.

Fig. 3 is a longitudinal cross-section through the plug and sleeve for the projectile showing the manner of their assembly.

Fig. l is a diagrammatic view of a portion of a well casing, cement lining and fluid formation showing the relation of projectile, screen plug and sleeve thereto.

Referring more in detail to the drawing:

1 designates a cylindrical projectile of suitable material having a pointed penetrating end 2 and a reduced neck end 3, Fig. 4.

Mounted on the neck 3 of the projectile is a screen plug 4 that is preferably of stainless steel fora purpose later explained. The plug 4 is of substantially cup shape and has an inner annular flange 5 the outer face of which is flush with the periphery of the projectile body. The plug 4 is preferably tapered outwardly toward its outer end in wedge-like serrations 6 that form in effect screw threads or welding surfaces for the plug. Perforations 1 of a size depending upon granulation of the formation are arranged in the head of the plug and are normally closed at their inner ends by the neck of the projectile.

If desired, a shear pin 9 may be passed through aligned openings in the plug and projectile to aid in holding them together.

I 0 designates a frangible sleeve or bushing that is preferably of aluminum and has a loose fit over the projectile and over the annular flange 5 of the plug to normally hold the same together. The sleeve I0 is preferably provided with spaced slots ll having closed ends I 2 adjacent the nose of the projectile and open ends 12 adjacent the plug.

Method and operation The method of using a projectile constructed as described is as follows:

A conventional gun (not shown) for perforating casing, cement linings and fluid formations is lowered into the casing M of a well hole [5 that has been lined with cement H5 or the like to hold the casing in a fluid formation I! that contains oil, gas or water.

The guns are usually provided with groups of muzzles, powder charges of suitabl varying strength and detonating devices and may be fired at will from the earths surface at the top of the Well.

Upon detonation, the projectile with plug and sleeve attached is blasted out of the gun through the casing to form a hole I8 in the casing with beaded edges 19 and 20.

It is a characteristic of stainless steel to weld itself to adjoining metal while being quickly sheared under high temperature; This characteristic is taken advantage of as the projectile pulls the larger head of the plug into the relatively small hole IS, the effect being to weld the plug in the hole as a substantially integral part of the casing.

As the projectile passes through the casing, the unslotted end of the sleeve it engages the inner face of the casing. Upon continued motion of the projectile, the plug forces the slotted end of sleeve outwardly by the wedges 6 on the plug to peel off the sleeve in leaves 2|, Fig. 4. The sleeve fractures, substantially as indicated at 22, and drops off the projectile into the well casing.

The shear pin 9 also fractures leaving the plug 4 in the casing; while the projectile proper continues on to form a fluid passage 23 in the cement lining I6 and formation [1. I

Fluid thus drains from the formation to the casing, but the casing does not "sand up because even though the formation may be unconsolidated, that is to say made up of loose particles such as sand, the perforations in the plug allow fluid to pass into the casing, but the plug screens the sand and other loose solid particles and prevents clogging of the hole or sanding up of the well.

.It is apparent, therefore, that I have provided an arrangement for effectively gun perforating unconsolidated formations in a facile, economical and efficient manner.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. In an apparatus of the character described, a projectile adapted to be fired from a gun in a Well casing, a screen plug on the projectile separable from the projectile upon engagement thereof with the casing, to lodge in the casing and plug the hole formed by the projectile, said plug having perforations of a size to pass fluids therethrough into the casing and exclude sand therefrom, a frangible sleeve normally surrounding the projectile, said sleeve having longitudinally arranged slots to facilitate peeling the sleeve off the projectile upon impact of the projectile with the casing, and a retaining pin normally connecting the plug to the projectile, said pin being frangible at stresses less than deformation stresses of the plug.

2. In an apparatus of the character described, a projectile, a separable perforated plug on the projectile, and a frangible sleeve normally surrounding the projectile.

3. In an apparatus of the character described,- a projectile adapted to be fired from a gun in a well casing, a screen plug on the projectile separable from the projectile upon engagement thereof with the casing to lodge in the casing and plug the hole formed by the projectile, said plug having perforations of a size to pass fluids therethrough into the casing and exclude sand therefrom, and a frangible sleeve normally surrounding the projectile, said sleeve having longitudinally arranged slots to facilitate peeling the sleeve off the projectile upon impact of the projectile wit the casing.

GERALD B. THOMAS, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER. REFERENCES Metals Handbook, 1939 Edition, Published by American Society for Metals, Cleveland, Ohio. 

